As generally accepted, the A-delta and C-fibers in the peripheral nerves are related to pain sensation. It has also been found that about 80% of the fibers in the vagus nerve are C-fibers presumably mediating the pain sensation from the visceral organs. In the present experiment the vagus nerve of the cat and of the rats are stimulated and extracellular and intracellular responses are recorded from the ganglion nodosum, nucleus tractus solitarius, dorsal nucleus of vagus, nucleus centralis lateralis and nucleus parafascicularis. In the same experiment, as the vagus nerve is stimulated, the sural nerve or saphenous nerve is also stimulated at different intervals in order to investigate the interaction of the impulses from somatosensory and autonomic nerves recorded from the various subcortical nuclei. Furthermore, as the vagus nerve is repetitively stimulated, changes in metabolism of the various nuclear structures were studied.